This invention relates to an automatic labeling machine of the type which has several curved glue pallets that are carried by a turret. The turret is driven rotationally at a constant speed to bring each pallet in contact with a glue application roller, and then to a stack of labels for picking one up and carrying it to a transfer cylinder wereupon the label is transferred to a bottle in a series of bottles that is being conveyed past the turret.
In machines of the type outlined, it is necessary to interrupt picking up of labels when there is an interruption in the series of bottles that are conveyed to the labeling machine in which case no bottle would be present for having the label transferred to it. Label pickup must start or stop synchronously with the supply of bottles to be labelled. When short gaps appear in the series of bottles, even a gap of just one bottle, label pickup must be stopped in relation to that bottle to avoid fouling the labeling machine with non-applied labels.
A labeling machine that is constructed to avoid picking up a label and, hence, avoid releasing the glue coated label when no bottle is present to receive it is described in U.S. Pat. No. 4,361,460 which issued on Nov. 30, 1982 in the name of one of the joint inventors of this application. In this patent in each pallet assembly there is a double-acting clutch member between a pallet shaft and a driven shaft that is for oscillating the pallet to properly position it and rock it at the glue application, the label pickup and the transfer cylinder locations. In one position, the clutch positively engages the pallet shaft and driven shaft for periodically oscillating the pallet from a radially retracted position to a radially extended position for successively contacting the glue application roller, the label source and label transfer cylinder. In its other position, the clutch member disengages the driven shaft and the pallet shaft and locks the pallet shaft to the turret, thereby retaining the pallet in its retracted position to pass by the label and prevent pickup and delivery of labels and glue. The clutch can be shifted from either position to the other only at an angular or rotational position of the turret in which the pallet is normally momentarily retracted and motionless with respect to the turret, so only an element of the clutch must be accelerated and decelerated to interrupt and resume the label pickup and delivery cycle. The movable element can have a very low mass and can thus be shifted quickly by applying a small force. The force is derived from pressurized air such that the clutch member is moved axially in the manner of a piston. In the patented apparatus, the slidable clutch member is splined to and slidable on a drive member which is in constant engagement with the pallet shaft by virtue of the drive member and pallet shaft being splined together. The dogs or projections on the clutch member that lock the pallet shaft drive member to the turret and the projections on the clutch member that lock the drive member to a cam driven shaft are on a common part, namely, the pallet shaft drive member. Thus, in one end position of the clutch member, the pallet shaft drive member is connected with the turret and prevented from rotating, and in the other end position the clutch member is connected to the cam driven shaft to thereby oscillate each pallet as is required for going through the glue application, label pickup and label transfer cycle. In this clutch arrangement, the pneumatically driven clutch member assumes an intermediate position in which the clutch member engages the pallet shaft drive member to secure it to the turret and prevent its rotation while at the same time the projections on the clutch member still bring about a connection between the pallet shaft drive member and the cam driven shaft. This intermediate position of the clutch member takes place during an interval when the turret and pallet drive member are standing still relative to each other as a result of the configuration of the cam that controls the driven shaft in this rotational position of the turret. The advantage of this arrangement is that the pallet shaft drive member and the cam controlled oscillating shaft are never allowed to rotate independently of each other so as to get out of synchronism. However, in the patented apparatus, it is conceivable that the slidable clutch member at the end of the interval during which there is no relative motion between the turret and pallet shaft drive member will not have completely reached its end position so that the parts will still be in engagement. This might happen, for example, if the air pressure which drives the clutch member is too low. Then, upon commencement of relative rotation between the cam-controlled shaft and the pallet drive member or turret, respectively, damage may occur in the clutch.
Another conceivable possibility is that the clutch member can be in the intermediate position temporarily and thus be completely free so that the pallet shaft is unlocked from the turret and the pallet shaft drive member is also unlocked from the cam-controlled shaft. In this case no damage could result but there could be an undesirable relative rotation between the pallet shaft and the turret or between the pallet shaft and cam-controlled drive shaft which would get the part out of synchronism.